User Agent Parser

A user agent string is a text identifier that web browsers and other HTTP clients send to web servers with every request. It is included in the User-Agent HTTP header and provides information about the client software, operating system, and device. Web servers and applications use this information for content negotiation, analytics, and compatibility checks.

Anatomy of a User Agent String

A typical user agent string follows a complex format that has evolved over decades. Modern browser user agent strings contain multiple product tokens, platform identifiers, and compatibility flags. For example, Chrome's user agent includes references to Mozilla, AppleWebKit, Chrome, and Safari, primarily for historical compatibility reasons. This layered format is often called "user agent string spoofing" because browsers mimic each other's identifiers to ensure they receive full-featured content from servers that check user agents.

Browser Detection

This parser identifies all major browsers including Chrome, Firefox, Safari, Edge, Opera, Internet Explorer, Brave, Vivaldi, Samsung Internet, and UC Browser. It examines specific tokens and their order in the user agent string to distinguish between browsers that share common components. For example, Edge includes the Edg/ token, while Chrome does not, even though both are based on the Chromium engine.

Operating System Detection

The user agent string reveals the client's operating system and version. This parser detects Windows (with version numbers mapped to marketing names like Windows 10 and Windows 11), macOS (with version numbers), Linux (including distribution hints), Android (with version numbers), iOS, iPadOS, Chrome OS, and other platforms. Mobile operating systems also often include device model information.

Device Type Classification

Determining whether a request comes from a desktop, mobile phone, or tablet is crucial for responsive web design and analytics. This parser classifies devices based on keywords like "Mobile", "Tablet", "iPad", and specific device identifiers. It also recognizes smart TVs, game consoles, and other non-traditional browsing devices.

Bot and Crawler Detection

Search engine bots and web crawlers identify themselves in the user agent string. This parser detects major bots including Googlebot, Bingbot, Yahoo Slurp, Baiduspider, DuckDuckBot, Facebook crawler, Twitter bot, and many others. Identifying bots is critical for SEO monitoring, rate limiting, and access control in web applications.

User Agent Client Hints

Modern browsers are gradually replacing the traditional user agent string with structured User Agent Client Hints (UA-CH). This newer approach uses HTTP headers like Sec-CH-UA, Sec-CH-UA-Platform, and Sec-CH-UA-Mobile to provide specific information on demand, improving both privacy and reliability compared to the legacy user agent string.

100% Client-Side Processing

All parsing in this tool happens entirely in your browser using JavaScript regex patterns. No data is transmitted to any server. Your user agent strings and parsed results never leave your device, making this tool safe to use with any user agent string.